1. Field of the Invention
The present invention relates to a lead frame for mounting thereon an optical semiconductor device in which an optical semiconductor chip is hermetically sealed and also relates to an optical semiconductor device using such a lead frame.
2. Description of the Related Art
An optical semiconductor device known in the prior art has such a structure that a silicon substrate, on which an optical semiconductor chip and a leading end of an optical fiber are fixedly mounted, is accommodated in a ceramic package (a package made from a ceramic material) or a metal package (a package made from a metal).
Although such a ceramic package and a metal package are advantageous in their sealing properties, they are expensive and not suitable for commonly used optical semiconductor devices.
In order to solve these problems, a hermetically sealed type optical semiconductor device has been proposed in which an optical semiconductor chip, such as LD (laser diode), PD (photo diode) or similar elements and a leading end of an optical fiber for, for example, emitting a light to the optical semiconductor chip are fixedly mounted on a lead frame and hermetically sealed with any suitable sealing material, such as molding resin, together with a part of the lead frame.
However, in such a hermetically sealed type optical semiconductor device, when the substrate, on which the optical semiconductor chip and the leading end of the optical fiber are fixedly mounted, is sealed with the molding material by a transfer molding process or an injection molding process, a relatively weak intermediate portion of the optical fiber, made of such as a silica glass and located outside of the substrate, may be pressed by the sealing material. Therefore, that portion may be deformed and a crack may be generated and, in some cases, a disconnection of the fiber may occur. In this case, the intermediate portion of the optical fiber can no longer effectively transmit the light.